THE WATER SPIDER 387 



It is very interesting to watch one of these spiders when it is 

 making its way towards a fly upon a wall or railing. The un- 

 suspecting fly is sitting upon the edge or the upper surface of the 

 raihng. The spider creeps along below, travelling for a few inches 

 with great caution, and then peering round a corner in order to 

 see whether its quarry has taken alarm, it gradually approaches a 

 little closer, and so on until, with a sudden spring, it pounces upon 

 its victim and inflicts the fatal wound. 



THE WATER SPIDER (Family Argyronetid^) 



Our next spider lives in the water, and is therefore called 

 the Water Spider. It is especially fond of clear, weedy ponds, 

 in which it is sometimes found in the greatest abundance. Like 

 water insects, moreover, it can remain submerged for some time. 



It breathes air, but it has no air-cistern, like the water beetles, 

 for it possesses no wing-cases beneath which a supply of fresh air 

 might be stored up. It has, however, a body thickly clothed with 

 long hairs; and when it dives, a number of little air-bubbles are 

 entangled among these, so that the spider can breathe with perfect 

 freedom. 



By means of these hairs, too, it brings the air-supply to the 

 odd little silken cell which serves as its nursery. This cell is 

 always placed beneath the surface of the water, and is fastened by 

 a number of threads, or " guy-ropes ", to the stems and leaves of 

 aquatic plants. In shape it is like a thimble, the mouth being 

 always below. 



Having constructed its nursery, the spider next proceeds to 

 fill it with air. This it does by ascending to the surface, and 

 then diving below with a quantity of air entangled, partly among 

 its long hairs, and partly between its hinder legs. Creeping 

 beneath the cell, it gives itself a shake, and so dislodges the 

 air, which floats up through the wide mouth, but cannot pass 

 through the closely - woven walls. A second supply is then 

 brought in like manner, and the process is repeated until the cell 

 is full. 



